336 MORPHOLOGY. 



or male organ, we might regard it as a male member of the flower, 

 and we should distinguish between organ and member. It is an 

 organ when we consider pollen production, but it is not a sexual 

 organ. When we consider fertilization it is not a sexual organ, 

 but a male member of the flower which bears the small spore. 

 The following table will serve to indicate these relations. 



Stamen = spore-bearing leaf = male member of flower. 



Anther locule = sporangium. 



Pollen grain = small spore = reduced male prothallium and 

 sexual organ. 



So the pistil is not a sexual organ, but might be regarded as 

 the female member of the flower. 



Pistil = spore-bearing leaf = female member of flower. 



O vule = sporangi um . 



Embryo sac = large spore = female prothallium containing the 



egg- 

 The egg =a reduced archegonium^the female sexual organ. 



Progression and Retrogression in Sporophyte and 

 Gametophyte. 



670. Sporophyte is prominent and highly developed. In the angiosperms 

 then, as we have seen from the plants already studied, the trillium, dentaria, 

 etc., are sporophytes, that is they represent the spore-bearing, or sporophytic, 

 stage. Just as we found in the case of the gymnosperms and ferns, this stage 

 is the prominent one, and the one by which we characterize and recognize the 

 plant. We see also that the plants of this group are still more highly sj ccial- 

 ized and complex than the gymnosperms, just as they were more specialized 

 and complex than the members of the fern group. From the very simple 

 condition in which we possibly find the Sporophyte in some of the alga.- like 

 spirogyra, vaucheria, and coleochsete, there has been a gradual increase in 

 size, specialization of parts, and complexity of structure through the Lryo- 

 phytes, pteridophytes, and gymnosperms, up to the highest types of plant 

 structure found in the angiosperms. Not only do we find that these changes 

 have taken place, but we see that, from a condition of complete dependence of 

 the spore-bearing stage on the sexual stage 'gametophyte), as we find it in the 

 liverworts and mosses, it first becomes free from the gametophyte in the mem- 

 bers of the fern group, and is here able to lead an independent existence. 

 The sporophyte, then, might be regarded as the modern phase of plant life, 



